Plastic and application thereof



ployed as the plastic.

. Patented Dec. 22, 1942 PLASTIC AND APPLICATION THEREOF William H. Lycan, Milwaukee, Wis, assignor to Pittsburgh Plate Glass Company, Allegheny County, Pa., a corporation of Pennsylvania bio-Drawing. Original application January 23,

1939, Serial No. 252,399. Divided and this application July 31, 1941, Serial No. 404,873

1 Claim.

The present invention relates to plastic compositions and notably to plastic compositions suitable for use as reinforcing layers between sheets of glass in safety glass.

One object of the invention is to provide'a plastic composition suitable for use as an interlayer in safety glass, which is clear, transparent, tough, and firmly adherent to the glass surfaces over a wide range of ordinary atmospheric temperatures.

A second object of the invention is to provide a composition of the foregoing type, which is stable in color and other characteristics upon aging and exposure to light and heat.

A third object of the invention is to provide a composition which is resistant to the action of moisture.

during service and it is desirable that it be resistant to moisture in order that it remain adherent to the glass at the edges of the finished plate and in order to prevent haze during service. The plasticizer must not sweat out of the plasti-- cized mass. It must also be strongly adherent to the glass and retain its strength and plasticity both at reasonably high and at reasonably low temperatures (e. g., within the range of 0- to Of all the innumerable compositions of vinyl I acetal and plasticizers that have heretofore-been suggested as interlayers for safety glass, only a" These and other objects will be apparent from I The lamination of plates or sheets of glass with a layer or layers of plastic material, inorder to provide a shatter-proof glazing material for automobiles, is well known.

For years nitrocellulose was commonly em-.

However, it was characterized by many objectionable features. For example, it was not self-adherent to the glass and required the use of a cement coating in order to obtain satisfactory bonding to the glass. More.- over, it tended to discolor to an objectionable degree upon aging under light. Its strength was also only fair and at low temperatures such as are encountered in winter in many parts of the country it became so brittle as to impart but little resistance to shattering to theglass in which it was incorporated.

Recently the use of polyvinyl acetals (reaction products of a hydrolyzed polyvinyl acetate with an aldehyde such as butyraldehyde) as reinforcements in safety glass has been suggested.

The preparation of a resin suitable for the pur pose has been described in Fix Patent 2,045,130 and in Patent 2,120,628 to Ernest W. Reid. The resin is greatly superior to nitrocellulose a a plastic layer in safety glass, but before it can be formed into sheets suitable for such use it must be modified by incorporation with a considerable amount of a plasticizer.

The provision of a plasticized mass suitable for use as the interlayer in safety glass involves much 5 triflinglv small percentage can meet the exacting requirement imposed. 'As a result of years of research, compositions of vinyl acetal and the hexoic acid esters of di and triethylene glycol have heretofore been selected as outstandingly successful as reinforcements in safety glass. Almost all others have heretofore been found to be impracticable. The use of this plastic composition as an intermedlatefor safety glass is disclosed in Patent 2,045,130 to Earl L. Fix.

The present invention is based upon the discovery that plastic compositions obtained by incorporation of mixed esters of glycols and certain acids with vinyl acetal resins are of outstanding merit for use as reinforcing layers in safety glass and in some respects are even superior to the corresponding plastics containing the glycol hexoate esters.

In the preparation of the plastics, vinyl acetal resins may be compounded with mixed esters;v of

various glycols including ethylene glycol, diethy'lene glycol, triethylene glycol and polyethylene glycols in general, and trimethylene-glycol. Glyeach other in molecular weight or in the arrangement of the carbon atoms in the molecule or in both. Preferably one of the acids is of relatively low molecular weight and contains from 2 to 5 carbon atoms. In the case' of butyric acid the.

molecule may-be of either straight or, branched chain. Any of the four possible valeric acids may be employed.:- These acids are employed in conjunction with higher open chain acids containin from about 6 to 14 carbon'atoms in normal or branched chain relation. Examples of these acids include caproic, caprlc acid, caprylic acid, lauric tain its clarity when theplastic is subjected to.

heat during lamination and upon subsequent aging and exposure to light. It must not form bubbles acid and any of the various isomers thereof.

Preferably the acids are admixed in equi-molar ratios and the mixture is reacted with an equivalent amount of a glycol such as-ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol or trimethylene glycol. A mixture of esters including a predominant amount .of a

without separation into components with vinyl acetal resins. However, the mixture may also be separated by distillation or other common methods into fractions which consist entirely of, or are enriched in, one or more of the components.

A specific example of a mixed ester is triethylene' glycol n-butyrate caprylate which was obtained by heating together equi-molar amounts of caprylic acid, n-butyric acid and the desired glycol in the presence of an acid catalyst, and continuously evaporating the water of reaction.

The reaction product comprises a mixture of the dibutyrate dicaprylate and caprylate-butyrate of triethylene glycol containing, for example, 50 percent of mixedester and 25 percent of the diesters of each of the acids. It was compounded with a vinyl acetal, e. g., a product obtained by treating polymerized vinyl acetate with butyraldehyde or other aldehyde. Such acetals are described in Reid Patent 2,120,628 or Fix Patent 2,045,130. The ester was incorbut higher and lower ratios, e. g., to 45 percent may be employed. Admixture may be effected in any convenient way. For example, the ester may be admixed with resin in an organic solvent, and the solvent evaporated. The plasticizer may also be milled into a mass of resin containing 5 or 10% of water. The plasticized resin was sheeted by extrusion or rolling at a temperature slightly below that of boiling water. The water was then evaporated. methods of incorporating the resin and the modifier are described in Haux Patent 2,046,378.

The sheets were assembled between sheets of glass without any intermediate cement and the assembly was preliminarily pressed by rolling to expel air bubbles. It was then laminated by direct application of fluid pressure of a medium such as ethylene glycol in an autoclave. The temperature of treatment was about 120 C. and the pressure was about 150 lbs. per square inch. These values are not critical. The above conditions were maintained for a few minutes and the autoclave was gradually cooled until the plastic had hardened to a certain extent. The autoclave was then opened and cooling was completed.

In the resultant product the plastic was clear and free of bubbles and blemishes and the ester did not .tend to sweat out or seggregate. It, also, resisted penetration by moisture and discoloration by ultraviolet light.

Similarly, glass sheets were laminated with vinyl' acetal resin in admixture with 31% of one of the following estersr a) Triethylene glycol isobutyrate caprylate. (b) Diethylene glycol isobutyrate laurate. (c) Diethylene glycol isobutyrate caprylate. d) Diethylene glycol isobutyrate caprate.

In any of the foregoing examples butyric acid may be replaced by other acids including valeric acids and propionic acid and acetic acid. Thus it, is possible. to .laminate sheets of glass with blends of vinyl acetal and di or tri or tetra ethylene or trimethylene glycol esters of lauric acid and acetic acid, lauric acid and propionic acid, caprylic acid and acetic acid or propionic acid, and various others of similar nature. r

Convenient Mixtures or blends of two or more of the mixed esters or of the blend of said mixed esters and the accompanying diesters are contemplated. The mixtures may be of equal parts or other convenient ratios.

Break tests were conducted by dropping a one- Triethylene glycol n-butyrate capryiate- 0 F. 70 F. F.

20 50 17 Triethylene glycol isobutyrate caprylate 0 F. 70 F. 120 F.

20 50 20 Diethylene glycol isobutyrate capryiate 0 F. 70 F. 120 F.

26 50, 16 Diethylene glycol isobutyrate caprate 0 F. 70 F. 120 F.

28 50 18 Triethylene glycol isobutyrate Caprate- 0 F. 70 F. 120 F.

The resistance of these samples to breakage at both high and low temperature is exceptionally good. All of the other essential qualities are also excellent.

The mixed esters obtained by reaction of a glycol with a mixture of two fatty acids, one of which contains 6 to 12 carbon atoms and the other of which'contains from 2to 5 carbon atoms, when incorporated into vinyl acetal-offer substantial advantagesover corresponding diesters of either of the components. For example, di-

esters of glycols with the higher acids, in admixture with vinyl acetal, tend to sweat out and produce failure of the bond to the glass. The diesters of the lower acids tend to become less effective at higher temperatures and are not sufliciently resistant to moisture. In contradistinction, the mixed esters do not tend to absorb moisture and do not sweat out from the plastic mixture.

As shown by the foregoing tests, the safety glass, in which the materials are used, is of exceptional strength and possesses to a remarkable degree all of the properties desired in a plastic so used.

This is a division of my copending application Serial No. 252,399 filed January 23, 1939, for improvement in Plastics and application thereof.

The forms and embodiments of the invention herein disclosed are typical examples. However, it will be apparent that numerous modifications can be made therein without departure from the spirit of the invention or the scope of the appended claim.

What I claim is:

As a new chemical compound, a mixed ester of a polyethylene glycol, with an acid of low molecular weight from the class comprising acetic acid, propionic acid, butyric acid and valeric acid and a higher acid from the class comprising caprolc acid, capric acid and caprylic acid, said compound being characterized by compatibility with and a capacity for plasticizing polyvinyl acetal resins.

WILLIAM H. LYCAN. 

